Fluid pressure actuating system



P1120714, 1943. ..s;sH-E 2,336,892}

'FLUID PRESSURE ACTUATING SYSTEM File d'Max ch 28, 1942 I 3 Sheena-Sheet 1 INVENTOR EVESCHNELL:

QBNEY.

Dec. 14, 19% s. SCHNELL 2 FLUID PRESSURE ACTUATING SYSTEM Filed March 28, 1942 5 Sheets-Sheet 2 INVENTGR A STEV SCHNELL.

ATTORNEY Dec, 14, 1943. s, sc 2,336,892

FLUID PRESSURE ACTUATING SYSTEM Filed March 28,.1942 3 Sheets-Sheet 3 FI G.3

' INVENTOR ST E V SCHNE L L BY ATTORNEY Patented Dec. 14, 1 943 UNITED STATES PATENT OFFICE.

Steve Schnell, Kirkwood, Mo.,

nei- Electric Corporation,

poration of Delaware Application March 28, 1942, Serial No. 436,635

(Cl. Gil-54.5)

14 Claims.

My invention relates to fluid pressure actuate ing systems and more particularly to a system in which a large volume of fluid can be displaced during the initial operation of the system and then'a smaller volume of fluid during later operation.

One of the objects of my invention is to produce an improved fluid pressure actuating system in which means are so associated with a master cylinder device that a large volume of fluid will be displaced to actuate a' device for each increment of movement of the piston of the master cylinder when said piston is moved through a portion of its protractile stroke and a smaller volume of fluid will be displaced for each similar increment of movement or the piston when it is moved through the remainder of its protractile stroke.

Another object of my invention is to provide a fluid displacing means for a fluid pressure actuating system which will result in the fluid pressure developed by the fluid pressure producing device, when initially operated, to apply pressure to and displace a large volume of trapped fluid to actuate a fluid motor and upon the attainment of a predetermined pressure to automatically result in the fluid under pressure in the pressure producing device to be placed in communication with the trapped fluid to continue the actuation of the fluid motor and in accordance with the volume of fluid being displaced by the pressure producing device.

Yet another object of my invention is to produce an improved fluid pressure actuating system which embodies means permitting a compounding action on the fluid pressure employed to actuate a fluid motor and to associate therewith means for limiting the fluid pressure which can be effective to actuate said motor.

Still another object of my invention is to embody a large volume displacing means in a fluid pressure actuating system which will automatically become ineffective to create fluid pressure when a predetermined pressure is obtained and subsequently return to its normally inoperative condition during the continued development of fluid pressure above the predetermined value.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawings in which Figure 1 is a schematic view or a fluid pressure actuating system embodying my invention, parts being shown insection; Figure 2 ls-a schematic view of another system showing in section a different construction of certain of the assignor to Wag- St. Louis, Mo., a corparts; and Figure 3 is a schematic view of still another system, the different parts thereof being shown in section. v

Referring first to Figure 1, the system disclosed comprises, as its essential units, a master cylinder A, a large volume fluid displacing means B, a pressure-operated control valve C, and an actuated device D.

The master cylinder device A is of standard construction and comprises a cylinder l in which is reciprocable a piston 2 said piston being operated by a piston rod 3 and a brake pedal 4. The piston is normally biased to its inoperative position by a spring 5 and when in this position, it uncovers a porthole 6 which places the cylinder in two-way communication with the reservoir l positioned above the cylinder. The outlet of cylinder I is connected by a conduit 8 and branch conduits 9 and III to the units B and C.

The device D to be actuated is shown,,by way of example, as a brake II, the brakeshoes l2 thereof being actuated by the fluid motor I 3. This fluid motor has connected thereto a conduit H which communicates at two points with the large volume fluid displacing means B by means of branch conduits l5 and I6. Another branch conduit ll places conduit ll incommunication with the pressure control valve means C. The large volume fluid displacing means B comprisesa casing l8 in which is provided axially aligned cylinders l9 and 2!! divided by a'partition 2|. The right end of cylinder l9 communicates with the branch conduit 9 leading from the master cylinder device, the connection being established by the fitting 22 which also acts as an end wall for the cylinder. The forward end of cylinder I9 is provided with an outlet port 23 which is connected to branch conduit IS. The forward end of cylinder 20 is connected to branch conduit I 5, the connectionbeing made by a fltv ting 24 which also serves as an end wall forcylinder 20. Mounted for reciprocable movement in cylinder I9 is a piston 25 having a packing cup 26 for preventing fluid from passing the'piston from theright end of cylinder ill to theleft end of said cylinder. Within cylinder 20 is a piston 21 having'a packing cup 28 for preventing fluid-from passing th piston from the left end of the cylinder to the right end. This packing cup, however, is capable of collapsing to permit fluid to pass the piston in the opposite direction, the flow of fluid being facilitated by the holes 29 in the piston.

Pistons 25 and 21 are connected together for simultaneous movement by a piston rod 30 which isof such length fitting 22 at the right end of the cylinder, piston .21 will be slightly 1 piston 21.

- duit 34 to reservoir'l; or the master vice A. Thus as piston 21 moves forwardly and i the volume of chamber 32 increases, fluid can" posed between chamber 32 of fluid in the opposite direction.

} shoulder "between limit the movement or andztheflarger cylinder ton 5.0;;the1argeend 5| being positioned in oy1in extension 43. Piston.

to. flow around element ,passes throug h the partition'2l. A spring 3| acts normally biases the pistonsto their cylinders. The piston rod that whenplston 21 abuts the on piston 21 and the right ends of spaced from partition 2| in order to provide a chamber 32 at the rear side of pistonlrod at partition 2! to preventuany'fluid iromflowing to chamber 32 from cylinder-i l9; In order that chamber 32'may be filled at all times with fluid, said chamber flow from the mastercylinder reservoir to chamber 32 and maintain this chamber fllled. Inter-v and conduit34 is a spring-biased check valve not appreciably restricting flow of fluidv from reservoir-1to chamber 32 but preventing any flow The pressure-operated control valve bodied in a casing provided witha bore 31 at 'one endand a Ts1ight1y 1arger central bore 38, "said bore '31 communicating with branch conduit ill leadingfrfromthemaster cylinder device. A

into casing 34 at the end opposite bore 31 and this fitting is provided-with b acylinderw. Asecond 'flttingliconnects this. cylinder with the previously referred-to branch. conduit-'lTwhich communicates'withfluid motor" Positioned for. limited recipl3 6! the brake. v

bore 31 is apiston'42 having rocable movement in a cylindrical extension 43-forming a chamber 44,. said chamber being in-communication with bore 31ahead of the jright end'orthe piston by means of a passage 45through the piston.

v The packing cup 46 seals the piston; The piston 42 is also provided with aiflange bores 31 and 38 in order to piston 42 to the right. A relatively strong springg49 surround the exten- 1 ion u and i interposed between flange n yfltting 39 to bias the pist'onto its extreme right position; .7

Cooperating with the I "is a two-diameter pisder l and-the small end 52 being positioned in rubber or like yieldable material and its 'Tcentral part is surrounded by a sleeve 53 cooperating with bothcylinder." and extension 43. A passage 54 extends through piston 50 and this passage is adapted to be closed under certain conditions by' a valveelement 55. A spring 56 biases this element so that it-will engage the end suria'ceof the large portion 5| of piston 50 which surrounds passage; The.element ;55.is capable of having only limited the fitting 39 and the oflement 55 is positioned. Fluid is permitted ,55 by way of the holes 58; in the flange. Flow offluid through holes 58 1 is restricted when.1element55 has engagement with fitting H.

,The piston 50 is normally held in engagement with element 55 by a spring 59 which is interposed between-the small end of piston '50 and the pistonJ42. This spring 59 is of greater'strengththan spring 56 which acts on r element 55. ;Spring 59determinestheiorce which A packing v cup 33 is provided for the 35, said check valve 5 41 for cooperation with the;

cylindrical extension 43 50.15 preferably madeyofmovement under the action ofspring j 55, said movement being determined by the space between a shoulder. 51 on I "other fitting 4| ,betweenwhich a flange portion actuate fluid motor i3 isconnected by a con-v V cylinder de- Cis em placed by piston 2 tel-cylinder device A a position :to close passage isnecessary to act upon the large end 5| of piston to move said piston to the right and cause passage 54 to be open.

Referring to the operation of the above described fluid pressure actuating system, all the elements or the various parts making up the units of the system will be infthe positions shown when the system is inoperative. When it is desired to to apply the device D, shown is a brake, the maswm be operated by actuatpiston 2 moves Sllfllwhich in the-instance ing the pedal 4. As soon as ciently to cut oil the port begin to be developed by the master cylinder device. .This fluid pressure will be efiective on piston; 25 of the large volume fluid displacing device B andalsoon pistons 42and 50 of the valve means C.v Since element in the valve means C is in 54, fluid under pressure cannot pass through said valve means C.

'The pressure acting on piston 5ll will maintain element 55" seated in the position shown. The fluid pressuredeveloped by the master cylinder .will beeffective ,in moving piston 25 to theleft and, or course, also piston 21 which is connected to piston; 25 by the connecting rod 30. As both pistons 25 and 21 are simultaneously moved to the lett, theywillbe effective in displacing fluid from their cylinders I9 and 20; which fluid will be efreservoir through pipe and past check valve 35.

- When the pressure in cylinders l9 and 20 and the connected lines reaches such a predetermined value that piston 55in the valve means C will be moved to the'right against spring 59,

",then .the fluid under pressure developed by the master cylinder will be directly connected with fluid motor l3, thus equalizing the fluid pressure in the master cylinder device and also in all the lines and the cylinders l9 and 20. When passage is first opened,'the fluid pressure acting on the large end 5i will increase rapidly and due to the larger area of end 5|, piston 50 will i be moved quickly to the rightagainst the spaced.

extension 43 and held in this position. 'When ,element 55 is unseated'from piston 50, the inrush of the higher pressure will force the element to the position shown where holes 58 are restricted. This restriction'of the flow of fluid pa'st element 55 .will result in the different fluid pressures equalizing slowly;

Continued movement of the piston of the master cylinder will now result in the fluid pressure being developedthereby becoming efiective in the fluid motor l3 and this motor will be actuated in the same manher as though the large volume fluid pressure displacing means B and the valve means C were eliminated. p When the valve means C becomes open and establishes equal fluid pressures on opposite sides 2 of piston 25, spring 31 will become effective to return this piston 25 andalso piston 21 to their normally inoperativepositions as shown in Fla- 6, fluid pressure will their areas are also equal to the.

on one piston. The pressure acting on piston 25will be twice the pressure ure 1. The fluid in chamber 32 will not prevvent rearward movement of both pistons 25 and 21 due to the fact that fluid can escape from this chamber past the packing cup 28' and into cylinder ahead of piston 21. As the spring 3| returns the pistons, the fluid displaced by piston will be forced down through open valve C to the opposite side thereof and also to the cylinder 20. The extra fluid necessary, to keep cylinder 21 fllled flows from chamber 32-past cup 28. The movement of piston rod will have no eflect in changing the-volume since, as

it moves into cylinder [9, it moves out of chamber 32. In other words, the total fluid containing space in cylinder 20 ahead of piston 21, in

' chamber 32, and in cylinder IS on both sides of piston 25 will always remain the same as the pistons move to the right. Since the p essure in all of this space is the same, the spring force is free to move the pistons. Thus it is seen that notwithstanding the continued actuation of the master cylinder device, the large volume fluid displacing pistons will return to their normally inoperative positions and be ready for a new stroke. v

As the master cylinder device continues to develop pressure, a predetermined value will be reached wherein the pressure acting on piston 42 of the valve means will be great enough to force this piston to the left aga-inst the action of spring 49. When this occurs, the piston will move and carry with it the double-headed piston 50. When pistons 42 andv have moved sufliciently to the left to cause the face of the large end of piston 50 to engage element and end connected to branch conduit 15 leading to -'.conduit I4 and fluid motor I3. Piston is moved by a smaller piston 62 slidable in cylinder In the unit 13 there is a single piston 60 for displacing the large volume of fluid which has an area equal to both pistons 25 and 21 of the previously described unitB.v This piston isposition'ed in cylinder 6| which 'hasits forward 63, this cylinder being connected to branch conduit 9 leading from the master cylinder device A. The pistons 60 and Marc biased to their retracted positions by a spring 64. The piston 60'is provided with apacking 60' preventing fluid from flowing from the cylinder ahead of the piston tothe rear of the piston but not preventing flow of fluid in the opposite direction. Therear; of piston 60 is in communicationwith the master cylinder reservoir in the same manner as in Figure The valve means C'-, comprises a casing having stepped bore 66 and 61. the smaller bore 6! being incommunication with branch conduit l0 leading from the master cylinder and the large bore 66 being in communication with branch conduit ll leading to conduit [4 and the fluid motor l3. Positioned within the stepped bores 66 and 61 is a double-headed piston 50having a passage 54' extending therethrough. This piston 50 is biased by a weak spring 59' to a poproduce a pressure between said face and the element suiflcient to prevent fluid-from flowing through passage 54. the master cylinder device will be disconnected from the fluid motor l3'and pressure in the motor will no longer be ,increased. Thus it is seen that there is provided'a safety means whereby the master cylinder device is prevented from developing an undesirable high pressure in the fluid motor. The maximum pressure that can be placed in the-fluid motor Willbe determined byspring 49 and the area of piston 42. v

When the master cylinder device is released, the fluidunder pressure in the fluid motor will return to the master cylinder device through the valve means C. As the piston of the master cylinder is. returned, the fluid. pressure on the right hand side of piston 50 will drop to zero and consequently the pressure effective on the opposite side of piston 50 will cause it to be unseated from valve element 55. The fluid will be free to flow back through passage 54 until the pressure has dropped to such an extremely low value that spring 59can cause piston 50 to again be seated against valve element 55.

If the master cylinder piston should only be partially retracted and then again moved forwardly when the fluid pressure in the system is below'the predetermined pressure at which the valve means 0 opens, pistons 25 and 2'l will again be operated until the pressure developed is great enough to open the valve means C in the manner already described. Referring to Figure 2, there is showna fluid pressure actuating system similar to that of Figure 1 except that the large volume fluid displacing means B has been replaced by a slightly sition wherein the surface of the large end of piston 50' engageselement 55' acted upon by spring 56 and having limitedv movement be tween fitting 4| and casing 65. l

. The operation of the system shown in Figure 2 is identical with that shown in Figure l with the exception that the entire fluid pressure which can be developed by the master cylinder device can be caused to be effective in fluid motor I3 since there is no pressure limiting means in the valve C. When the master cylinder device -A is initially operated, fluid under pressure will be effective to move pistons 62 and 6D forwardly and cause the large piston-60 to displace a large volume of fluid into the lines in the master cyllnder device. When a predetermined pressure is reached in fluid motor l3 and in lines l4, I5

and I1, piston 50' will be moved to the right to thus open up the passage 54' and thereby place the master cylinder device in direct communication with the fluid motor. This will cause the-fluid pressure acting on pistons 62 and-6O to become equal and since piston 60 is assumed to be twice the area of piston 62, said pistons different unit B and the valve means C has been replaced by a valve means C in which the high pressure safety means is eliminated.

will be moved to the right. The fluid at the rear of piston 60 which has passed check valve 35 will flow past the packing .cup. 69 as piston 60 moves rearwardly. I

In the fluid pressure actuating systemv shown in Figure 3, the-large volume fluid displacing means and the pressure control valve means have been combined into a single unit E where a sin- 7 gle large piston is employed to displace a large volume of fluid.

. I Referringnow to the specific construct on of this single unit, it comprises a casing 68 provided with a large cylinder 69 and a smaller cylinder 10. The large cylinder is connected to conduit l4 leading to the fluid motor 13 and the small cylinder is connected to conduit 8 leading from the master cylinder device A. The.

large cylinder 69 has mounted therein a piston Hand the small cylinder -l0 has mounted therein a piston", said pistons being connected by an integral sleeve 13 provided with stepped bores 14 and 15. A spring 16 biases the pistons to theirretracted positions as determined by the motor. The pressure of the master cylinder and shoulder 11 which'is engaged bythe large piston. The large piston has associated therewith past the piston from the-portion of the cylinder ahead of the pistonbut does not prevent flow in the opposite direction'g' The piston 'lzyhas associated with it a packing cup I8 for preventj ing fluid fromflowingpast the pistonfrom the right endof cylinder 18; Thecasing 68 isformed 'to provide a reservoir 88'above cylinder 88and the lower pressure in cylinder 58 will equalize' slowly due to the smallpassage 88. The pressure ton H is greater than'lthat of piston 12, the pistons will be moved to the right by a superior fluid force acting on piston "and also by the action of spring '18. The fluid which has enteredthe this reservoir is in direct communication with "the reservoir of the master cylinder device by wayof a conduit ill} The reservoir 88 com I municates with the extreme rear' end of cylinder 88 by means of a passage 82 and-a check valve 83 prevents fluid from returning to the reservoir 'fromthe rear end of said cylinder.

Slidably mounted within the stepped bores 14 and I5 is a two diameter piston having a through passage 85. The forward end of piston 84 isadapt-ed tocooperate with a valve elemerit 88 which is'fcarriedlby amember 8'l'and variable volume chamber at the rear of piston H during the movement of the piston forwardly will be pushed past the sealing cup 18 into the '12 again reach their normally inoperative positions,as shown in the" figure, passage 85 will continue to remain-open'fdue to the different forces acting-on piston 84 and also because spring 81 i cannot act on plunger 82 "as the fluid pressure being developed by the master cylinder holds spring 81 compressed.

When'it is desiredto release the brakes, the

" brake pedal is released and fluid from the fluid motor returns to the master cylinder. When the backed bya spring 88'. 1 A small? passage 88 through the piston and-a passage 80. through member'8'l perm t the large end of piston 84 1 cylinder '16'."

to be subject .to the fluid pressure in the large in order that the small end of piston 84 may fluid pressure falls to such a low value that spring 8] can be effective to move piston 82 to a position against stop 88,-'it will again be effective in moving piston 84 forwardly so that valve element 88 will be'seated, thereby closingpassage 85 and Being'aware 'of the possibility of modifications in the particular structure herein described without departing from the fundamental principles ton 121s a plunger 82, the-innerend of which n cooperates with the small end of piston 84 and the'outer end of whicliis adapted to engage a" piston 83 which is slidable'in a -bore 84 carried by the closure plug 85 forthe end of cylinder' 10; The piston 83 has associated therewith a sealing eleme'nt'88 and is backed by. aspring 81 which normally biases the pistonto engage a element Figure 3, when the master cylinder A- is actuated, fluid pressure will be developed and become eflective on'pistons 12,784 and183, This pressure, will stop 88. By means of this construction it is seen that when pistons H and 12 are in their normally inoperative positions asshown, spring 81 will I maintain piston 84 in engagement with valve 85' in order'to 'close passage 85 through the piston. 4 8 3 Referring to the operation of the structure of maintain piston 84 engaged with valve element F 88 and no fluid; can pass through passage 85. I

I The fluid pressure will also move piston 88 against spring 81' and relievethe-plungerz82of any actionof spring 81. Ascfluidpressure con-- tinues to be developed by the mastercylinder 12 will be .moved to the left as will large 'volume '01 fluid being displaced into line l4 85 to be opened by pressure in passage; 85 and then as the pressure in bore 14 increases, piston "84 w ll move to the right, thus preventing valve element 86 from reseating. The passage 85 will now be open and the master cylinder device placed in direct communication with the fluid claims.

of my invention, I do not intend that its scope be limited except as set forth by the appended Having runy described my invention, what I c laimas new and'desire to secure by Letters Patent of the United States is:

1. In a fluid pressure actuating system, a fluid motor for actuating a device, a source of pressure, a body offluid for placing the source in communication with the motor, means for'cutting ofi the source from communication with a portion of the body of fluidwhich is in communie cation with the 'motor'but only when the pressure in themotor is below'a predetermined value,

1 means for transferring pressure to' the portion 01 the body of fluid acting on the motor from that portion of thebody of fluid acted upon by the source of pressure but only when the cut-oft ;means is operative, said last named means comprising a movable member having different areas in contact with the cut-oil. portions of the body of fluid, and means for returning themovable member to its starting position when the cut-off means becomes inoperative and the motor is being operated by fluid pressure being directly communicated from the source. 7

2. In a fluid pressure actuating system, a fluid motor for actuating a device, a master cylinder device connected to communicate with the motor, means for preventing said communication when the pressure being developed by the m-aster cylinder device is below a predetermined value, a fluid chamber connected to the motor, a movable member for developing fluid pressure in the chamber to thereby operate the motor, means for causing the fluid pressure developed by the master cylinder when below said predetermined value "to move the movable member to thereby develop pressure in the chamber and motor, and means for returning the movable member to its nonpressuredeveloping system when the master cylmotor. for actuatin a device/two cylinders 01 inder operates the motor asa result of a direct communication therewith.

3. In a fluid pressure actuating system, a fluid motor for actuating a device, means comprising a movable member for developing fluid pressure to operate the motor, amas'ter cylinder device,

motor for actuating a device, a fluid chamber connected to the motor, a movable member for developing fluid pressure in the chamber to there- 'by operate themotor, a master cylinder device,

means for moving the movable memberirom a normally inoperative position by fluid pressure developed by the mastercylin'der device to. there- 'by develop 'fluid pressure to operate theinotor,

means for connecting the master cylinder device directly with the fluid motor .when the fluid pressure effectivein the fluid'rnotor is above,a'predetermined value, and means for returning the equal diameters each connected to the motor, a piston movable in each cylinder for developing I flu.d pressure to thereby operate the motor,

means connecting the pistons together for simultaneous movement, a fluid motor ior'actuating' the pistons and comprising a pistonhaving an area equal to the area of the first named pistons,

means for connecting said last named fluid motor to the master cylinder device for operation by fluid pressure developedby said master cylinder, and means for connecting the master cylinder device directly with the first named fluid momovable member to its normally inoperative position after the master cylinder device is directly connected to operate the motor and without a tor when the fluid pressure effective in said fluid motor is above a predetermined value.

' 8. In a fluid pressure actuating system, a fluid motor for actuating a device, two cylinders of equal diameters each connected to the motor, a piston movable in each cylinder for developing fluid: pressure to thereby operate the motor, means connecting the pistons together for simultaneous movement, a fluid motor for actuating the pistonsand comprising a piston having an area equal to the area of the first named pistons,

, means for connecting said last'named fluid motor to the master cylinder. device for operation by fluid pressure developed by said master cylinder, means for connecting the master cylinder device directly with the first named fluid motor when the fluid pressure'eflective in said fluid motor is above a predetermined value, and means for returning the two first named pistons to their nordecrease in the fluid pressureeflective in the fluid motor. L

5. In a fluid pressure actuatingsystem, a fluid connected to the motor,,a mastercylinder device connected to communicate with themot'or, means for preventing said communication when the pressure developed by the master cylinder device is below a predetermined value, a movable member for developing fluid pressure in the chamber to thereby operate the motor, a fluid motor having its movable member connected to the first named movable member, means for causing the bers to their non-pressure developing positions when the master cylinder communicates directly with the device actuating motor and functions to operate it.

6. In a fluid pressure actuating system, a fluid motor for actuating a device, two fluid chambers connected to the motor, a movable member in each chamber for developing fluid pressure therein to thereby operate the motor, means for connecting said members together for simultaneous movement, a master cylinder device, means for operating the movable members by fluid pressure developed by the master cylinder device and comprising a movable member having an area less than the total area of the flrst named movable members, and means for connecting the master cylinder device directly with the fluid motor when the fluid pressure effective in the motor is above a predetermined value.

mally inoperative positions after said mastercylinder device is directly connected to the flrst named fluid motor and functioning to operate "it, 'said lastnamed means embodying means for l I motor for, actuating a device,-a fluid chamber preventing a decrease in the fluid pressure eflective' in the ,flrst named fluid motor as said pistons are moved to their inoperative positions.

9. In a; fluid pressure actuating system, a fluid motor for'actuating'a device, a master cylinder device connected to communicate with the motor, means for preventing said communication when the pressure being developed by the master cylinder device is below a predetermined value, a fluid chamber connected to the motor, a movable member for developing fluid pressure in the chamber to thereby operate the motor, means for causing the fluid pressure developed by the master cylinder when below said predetermined value to move the movable member from its normally inoperative position to thereby develop pressure in the chamber and motor, means for returning the movable member to its normally inoperative position after the master cylinder is.

connected to communicate with the motor and functions to operate it, and means for injecting,

fluid into the chamber as the movable member is returned, said injected fluid having the same pressure as the fluid already in the chamber.

10. In a fluid pressure actuating system, a fluid motor for actuating a device, a master cylinder device connected to communicate with the motor, means for preventing said communication when the pressure being developed by the master cylinder. device is below a predetermined value, a fluid chamber connected to the motor, a movable member for developing fluid pressure in the chamber to thereby operate the motor, means for causing the fluidpressure developed by the master cylinder when below said predeter mined value to move the movable member from its normally inoperative position to thereby develop pressure in the chamber and motor, means predetermined-value 3 mally inoperative position aiter the master cylinder is connected to communicaterwith. the-mo v V tor, means for injecting fluid into the chamber? in v as'the movable member is returned, sai'd injected "fluid having the same pressure as-v 'the: fluid alreadyin the chamber,- and means for prevent-1 ing the master cylinder device, from communicatin'gi directly with the fluidmotor when-the 9 pressure being developed therebyreaches a? predetermined value greater than theg flrstnamed the master cylinder device. v means iot, directly connecting the master cylinder deviceto the motor when the pressure effective inthe motor is a predetermined value;,means for maintaining a body or fluid at the'r'ear of the pistomi imeans for permitting said fluid 'to passsaid istqn and enter thejcylinder ahead thereof when-the pg-s ton isv permitted to return to its normally ino perative position, and'means for returning said' piston when the master cylinder device" isvdirectly' connectedto the' motor and 'functioningtode-' velop pressureeffective-therein.

12. Ina flud pressure actuating systemQafluid' motor Ior actuatingja devicqaxially aligned .cy-l-* inde'rs of different diameters, interconnected-pisa tons in said cylinders a master ,cylinder'devicei conduitmeans'ior piacing'the, larger cylinder incommunication' with ,the motor, conduit ,means motor for ,actu'atinga device, a -cylinder'con nect'edto' the fluid motor', a' piston inzsaid cyl-" inder; a master cylinder device, means forxmo'v-- ing said piston byfluid pressure developed by for returning the movable member toits nora- I opposite direction;

and spring means for: returning the" pistons to their starting, positions when the master cylinder" device is placed directly in communication with; the motor and functioning todevelop pressureefl'ective' therein.

13. In a fluid pressure actuating'system; a fluid motor foraactuati'ng a (device, axially aligned cylinders'oi different diameters, interconnected pistons irr said'ncylinders, a master cylinder device, conduit means for placing the large cyiinder in communication" with the'motor, conduit means forfplacingnthe smaller cylinder in communication with the master cylinder device, means ior' directly connecting-{the master cylinderidevice to 'themotor when the pressure effective' in the. motor isapredetermined value, means iormaintaining'ab'ody; of fluid at the rear of the large piston; and'means for permltting'said fluid topass. said piston and enter the cylinder ahead thereof but preventing passage'of fluid in the 14, Ina fluid pressureactuating system, a fluid motor :Ior. actuating a device, means ior'develop- 1 ing; fluid-1 pressure to operate the motor, a master cylinder device, means' for; operating'the first,

named means: by fluid pressure developed by the master cylinderdevice, means comprising a pressure-operated valve having alvalve element movable trout-closed position too'pen position for die rectlygplalcing'the master cylinder device in communication withfthe" motor when the pressure effective" in. the motor is a predetermined value,

and means for closing said valve element when the pressurev developed by the master cylinder reaches a predeterminedvalue greater than the as for placing the smaller cylinder in comuiunicafirst named predetermined value, said lastnamed means comprising a piston associated with the valve element and acted upon by the master cylind'eridevelbped fluid pressure and 'a spring re-- sisting the movement of the piston to" closethe valve: element. i

i STEVE SCHNELL. 

